1. Field of the Invention
The present invention relates to a method of dividing a workpiece such as a semiconductor wafer into small square pieces even if some adjacent square pieces are not completely separated.
2. Related Arts
Referring to FIG. 9, a workpiece to be diced such as a semiconductor wafer W is attached to an associated frame F with an adhesive tape T to provide a workpiece-and-frame combination. As shown, the semiconductor wafer W has a lattice-like pattern defined by crossing streets S, each square area in the lattice containing a circuit pattern. The wafer W is cut into separate squares to provide pellets P, as seen in FIG. 10.
Referring to FIG. 11, the individual pellets P remain on the adhesive tape T, which is stretched across the frame F. The diced wafer-and-frame combination is washed to remove minute debris, and then the diced wafer-and-frame combination is transported to the pellet picking-up station where individual pellets P are removed from the adhesive tape T. It is transported to follow sequential manufacturing stations. Transportation of pellets in the form of diced wafer-and-frame combination is convenient, compared with transportation of individual pellets after being separated from their frames.
Transportation of diced wafer-and-frame combinations, however, has some defects attributable to use of adhesive tapes.
If some adjacent pellets are not completely separated from each other in cutting a semiconductor wafer, such pellets cannot be removed individually when being peeled off from the underlying adhesive tape.
Even if the semiconductor wafer is cut completely, the pellets are so close to each other that some adjacent pellets may be put in contact with each other when the adhesive tape is somewhat loosened (see FIGS. 12A and 12B), and then, such adjacent pellets are apt to rub against each other, causing cracking or damaging of pellets on their adjacent edges. This accident is likely to take place on the way to subsequent manufacturing station.
Minute debris remaining between adjacent pellets are difficult to be removed in washing, and pellets can be contaminated with such minute debris when they come up to the upper surfaces of some pellets later.
There has been, therefore, an increasing demand for an improved dicing method capable of providing diced wafer-and-frame combinations which are guaranteed to be free of such defects as described above.
To meet such demand a method of dicing workpiece by using a dicing apparatus comprising at least a chuck table holding workpiece attached to a frame via an adhesive tape, and dicing means for cutting a workpiece into small square pieces, said method comprising the steps of: cutting the workpiece into small square pieces in the state of being held in the frame; and ejecting a blow of air from the surface of the chuck table to the cut workpiece to expand the adhesive tape in the semispherical form.
The dicing method may further comprise the step of, subsequent to expansion of the adhesive tape, expanding the inter-spaces between adjacent small square pieces to keep them apart from each other still more.
Workpiece may be semiconductor wafer.
The dicing method according to the present invention assures that: the adhesive tape is expanded and stretched to make adjacent pellets to be separated from each other, thereby separating completely some adjacent pellets from each other even if they are partly contiguous, preventing any physical interference of adjacent pellets and permitting complete removal of minute debris from the inter-spaces between adjacent pellets.
Other objects and advantages of the present invention will be understood from the following description of a dicing method according to one preferred embodiment of the present invention.